be quiet! 350w SFX Power PSU

Simulated Load Testing

To provide accurate and consistent results in all of our PSU testing, Overclock3D uses professional grade DC electronic load equipment capable of placing a sustained load of 3690w across a total of six rails (including +5vsb and -12v) on the PSU! This is achieved by using a combination of SunMoon and Analogic electronic load equipment which allow us to adjust amperage loads in increments as small as 0.01A while also measuring voltage and wattage readings on-screen.

During today's tests, we will be placing the be quiet 350w SFX PSU under 25%, 50%, 75% and 100% load levels at room temperature. Unfortunately, due to the size of the PSU on test today no 50°C 'hot-box' testing could be performed.

be quiet! 350w SFX Results @ Room Temperature

+3.3v

+5.0v

+12v

+5vSB

-12v

AC Watts / DC Watts

Efficiency

Intake / Exhaust

Δ Temp

T1 (Low)

3.75A

4.00A

4.25A

0.62A

0.12A

105w / 88w

83.80%

27.2°C / 44.2°C

17.0°C

3.37v

5.09v

11.92v

5.14v

-11.90v

T2 (Med)

7.50A

8.00A

8.50A

1.25A

0.25A

205w / 176w

85.85%

27.0°C / 45.0°C

18.0C

3.35v

5.03v

11.94v

5.05v

-11.93v

T3 (High)

11.25A

12.00A

12.75A

1.87A

0.37A

309w / 263w

85.11%

26.5C / 45.8°C

19.3°C

3.33v

4.98v

11.94v

4.96v

-11.98v

T4 (Full)

15.00A

16.00A

17.00A

2.50A

0.50A

419w / 350w

83.53%

25.6°C / 44.7°C

19.1°C

3.31v

4.92v

11.96v

4.88v

-12.01v

T5 (x-load)

15.00A

16.00A

1.00A

0.00A

0.00A

175w /

138w

78.85%

27.2°C / 45.2°C

18.0°C

3.34v

4.75v

12.45v

5.16v

-12.50v

T6 (x-load)

1.00A

1.00A

29.50A

0.00A

0.00A

0w /

346w

00.00%

00.0°C / 00.0°C

0.0°C

0.00v

0.00v

0.00v

0.00v

-0.00v

T7 (MAX)

15.00A

16.00A

23.00A

2.50A

0.50A

507w / 420w

82.84%

27.3°C / 56.0°C

28.7°C

3.31v

4.93v

11.88v

4.86v

-12.06v

Starting with the results from Test 1-4 which best represent the PSU under normal usage, we can see that the +3.3v and +5v rails on the unit are reasonably stable with a drop of 0.06v and 0.17v respectively. The real shock however comes when we take a look at the results from the +12v rail which actually INCREASED by 0.04v from idle to full load. This normally occurs when the voltage regulation on the PSU overcompensates for the load and can actually end up reducing the total power output as a result. Efficiency, on the other hand is very good for such a small unit with 85% being achieved at a load of 180 - 260w.

Although it is quite unlike me to comment on the noise of a PSU given how loud the load testing equipment is, this is undoubtedly going to be an important factor in the decision of anyone purchasing a SFX PSU. Therefore, using my ear alone as the only measuring device, I can tell you that up to 200w load the SFX Power is very quiet. However as the load increases to 260w the 80mm fan speed increases significantly to the point where I imagine you'd easily be able to hear it across the room. At 350w I could actually hear the PSU above the load testing equipment, which is never a good sign!

T5 moves into the cross-load teritory and here we can see that the be quiet isn't so happy with a heavy load on the +3.3v and +5v rails and only a small load on the +12v rail. Voltages for the +5v rail hit a rather poor 4.75v and the +12v rail shoots up to 12.45v. Additionally efficiency during this test drops to around 78%. In T6 the cross-load is reversed with a minimal load being placed on the +3.3v and +5v rails and the rest on the +12v rail. Unfortunately during this test the be quiet unit refused to power on with anything above 25A on the +12v rail and therefore failed the test. What we do need to remember at this point though is that these cross-load results are highly unlikely to be reproduced by any PC system (especially a HTPC/SFF PC) in the real world. Only if you was intending to use the unit purely to power 12v devices and nothing else would this become an issue.

T7 sees the SFX Power hit a maximum output of 420w - 70w higher than that if its rated output. Given the size of the unit this is actually pretty respectable and shows that the unit has a little extra power to give should the need arise. At this load the voltages are still very respectable and efficiency is just shy of 83%.

be quiet! 350w SFX Scope Results @ Room Temperature

+3.3v

+5.0v

+12v

T1 (Low)

T2 (Med)

T3 (High)

T4 (Full)

T5 (x-load)

T6 (x-load)

T7

(MAX)

For those of you not familiar with the term 'ripple', this refers to the small fluctuations in voltage that occur in all PSU's on a milisecond scale. Large quantities of 'ripple' on a PSU can damage or kill components in your PC over time and therefore testing a PSU's performance in this area is just as important as any other part. Unfortunately ripple cannot be measured using a standard multimeter and requires a specialist device called an oscillioscope. The results you see above are taken from our Rigol 25Mhz 400MSa/s scope that can save 'screenshots' of its data to a USB memory stick.

A quick glance at the graphs above shows the most unruly rail to be the +3.3v one. However, even here the SFX Power manages to keep the ripple at just over 40mVpp in Test 4 and just under 40mVpp in Test 7. The +5v and +12v rails perform even better in comparison topping out at 21.6mVpp and 25.6mVpp respectively during Test 4. Only during the cross-load testing in T5 does the +5v rail break 50mVpp showing that the SFX Power isn't too keen on cross-load situations.

@Peter/VB, yeah I doubt in most systems it will come close to 350w so the high load noise won't really be too much of an issue. But on the other hand I do have a Q6600 HTPC with a HD4850 and 3x1TB HDD's, so I might give it a slightly hard time Quote

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